Repeater station



Sept. 2., 1941. I 3 MAGGIO 2,254,377

REPEATER STATION Filed 0Gt. 1.2, 1959 INVENTOR J 8. MAGGIO ATTORNEPatented Sept. 2, 1941 UNTES'TES 10 Claims.

This invention relatesto a repeater station or installation for atelephone system, and, more particuiarly, to a power. supply arrangementfor a multiplicity of amplifiers at such astation.

An object of this invention is to simplify and reduce the expense ofamplifier circuits for telephone systems.

A feature of the invention compn'ses operating a plurality ofstages ofan amplifier with their plate circuits in series, and utilizing theseries-connected stages as a potentiometer or voltage divider to providea desired potential for a specific electrode of oneystage of theamplifie-r.

Another feature comprises providing a multiplicity of such amplifiers ata repeater station and connecting them in multiple 'at the point in eachpotentiometer from whichis obtairied the potential for the specificelectrode of one stage of each amplifier. Y

Other andfurther features will. be apparent fromthe general-and detaileddescription which follows.

In accordance with the invention, anamplifier may comprse aplurality ofamplifying stages utlizing electron discharge devices, at least twostages having their plate circuitsconnected in series, and including apower stage having an electron discharge device withagrid auxiliary toits input control grid. A, eonneetiori is made from a point intermediatethe series-connected wire telephonepars. Each amplifier is similar indetailto amplifier V The amplifier A is connected ih=the cominunicationcircuit through input and.output transformers il), |2, and'comprisesthreestages' ci amplification provided; by amplifyng electrondischarge devices I4, Iii; [8. These devices are sh0Wn as pentodes, butthe initial two stages could be triodes, screen grid" tubes, or othermultigrid devices. The finaistage is' a-power stage, and, preferablycomprisesia s'creen grid or other multgrid tube. ;neithe'r eVent, the

cathodes may be of the directly or indirectly heated type. The screenvoltage of the power tube is lower than that of the plate; forcomparatively high power outputs With 1ow plate currents this is, ingenera], necessary.

The initial stages of the amplifier A have their space current circuitsconnected in series, the anode of device I! being directly connected tothe input centrol grid of device !6, the interstage network N1 beingproportioned so that its resistance component is sufficient to providethe desired biasing potential for the-control grid of device l. Althoughthe conventional blocking condenser between the devices M, 16 has beeneliminated, the circuit does not constitute a direct-current amplifier,since the infinite impedanceat zero frequency of by-pass condenser Creduces the gain to zero. The gain is not reduced, however, until thereactance of the condenser is comparable to the internal resstance ofdevice H3. Basing potential for the control grids of devices l4 and l8may be provided in conventional mannr, i. e, either by cathoderesistors, or by biasing batteries. interstage network N2 and blockingcondenser 20 couple the output circuit of device Iii and the inputcircuit of the power stage. Space current for the amplifiers A, B, C Nis provided from a common source 30, which, as shown, may be a storagebattery, or the filtered output of a reatifier, or a motor generatorset. This source 30 may be at the repeater station, or it may be at aremote point, e, g., another repeater station, or at a terminal of thesystem. Space current for the first two stages of amplifier A issupplied conductors 52, '44. If the battery 30 has its midpointgrounded, the point in each amplifier may be connected to a commonground. The screen grid of tube M s connected to the point 439 throughfiltering resistance 46, and that of tube 16 to the high potential endof the network N2. k

The arrangement desci*ibed is particularly advantageous in a carriertelephone system in which one or more auxiliary and unattendedrepeaterstatons are provided between main or A sutable terminal and attendedstations and the p1ate power supply balanced to ground at the auxiliarystation is furnished from a main station, the power supply ground,however, not being carried over the cable connecting the stations. Theoutput or power stage of the repeater station amplifiers may be operatedat the full supply voltage, that is, for example, the plate or anodewould be 125 vo1ts above ground and the cathode 125 vo1ts below groundwith a plate supply of 250 volts at the repeater station. Theconventional procedure with reference to the voltage ampli-- ficationstages would then be to reduce the plate supply to a value suitable tothe voltage amplifier tubes by means of a series resistance common tothe station, thus introducing a power loss.

With the arrangement of this invention, however, the space currentcircuits of the first and second stages of the amplifier are connectedin series so that approximately one-half of the plate supply voltage isapplied to each tube. Since the tubes are in series, their spacecurrents must.

be the same. The value of the space current Will be determined by theresistane of the interstage network N1, and the amount of bias on theinput control grid of the first tube.

Although the voltage distribution and space current w1'11 vary from tubeto tube used in the voltage amplification stages, this effect issubstantially eliminated by the multiplying of point 40 throughout therepeater station. With screen current of the output tube not tuo great,this point is a conVenient source of screen supply for the output tube.

Although this invention has been disclosed with reference to a specificembodiment, it is to be understood that its scope is limited by theappended claims only.

W'hat is c1aimed 15:

1. An electric wave amplifier comprising a plurality of amplifyingelectron discharge devices with their space current circuits connectedin series and so that the space current in eachis the same, and anadditional amplifying electron discharge device having a screen grid andwhose space current circuit is independent of that of said pluralty ofdevices, said plurality of devices constituting a potentiometerproviding potential for said screen grid.

2. A11 electric wave amplifier comprising a piurality of electrondischarge devices with their space current circuits connected inseriesand so, that the space current in each is the same, anotherelectron discharge device having its space current circuit independentof that of said piurality of, devices and 'having an input control gridand an auxiliary grid, and a connection from a point in said seriesconnected devices to said auxiliary gridto provide operating potentialfor said auxiliary grid.

3. A transmission system comprising a multiplicity of electric waveamplifiers, each amplifier comprising apair of electron dscharge deviceswith their space current circuitsconnected in series such that the spacecurrents in the devices are the same and such that approximately onehalfof the anode supply voltage is applied to each device, a common powersupply for said amplifiers such that substantially the same voltage issupplied across the series-connected pair of devices in each amplifier,the replacement of a:device by another tending to alter the Voltagedistribution between the pair of devices and the space current in theseriespath of a pair of devices, and means connecting said amplifiers inmultiple at a point in the circuit of each intermediate its devicessubstantially to eliminate such tendency.

4. A transmission system comprising a multiplicity of electric waveamplifiers, each amplifier comprising a pair of electron dischargedevices with their space current circuits connected in series such thatthe space current in each device is the same, each amplifier a1socomprising an output electron discharge device having a grid auxiliaryto its input control grid, a common power supply for said amplifiers,connections for applying the full potential of said supp1y between thecathode of the first and the anode of the second of the series-connecteddevices of each amplifier, and between the cathode and the anode of saidoutput device, said amplifiers being connected in multiple at a point inthe circiiit of each intermediate said series-connected devices, and aconnection from said intermediate point in eaohamplifier to theauxiliary grid of its respective output device. y

5. An ele ctric wave amplifrer comprising a pair of electron dischargedevices each having a cathode, an anode and an input control grid, asource of space current connected between the cathode of one device andthe anode of the second device, a direct connection between the anode ofsaid one device and the grid of the second device, a connection throughari interstgenet- Work from the anode of said one device to the cathodeof said second device, thespace current circuits of said devices beingconnected in series and said network having a resistive component thepotential drop across which provides biasing potential for the grid ofsaid second device, av

third electron dischar-ge device comprising a. cathode, an anode, aninput control grid, and an auxiliary grid, and a connection fro'm'thecathode end of said interstage network to said auxiliary grid.

4 '6. A11 e1ectric wave amplifier comprising a pair of electrondischarge devices each having a cathode, an anode and an input controlgrid, a source of space current connected between the cathode of onedevice and the anode of the second device, a direct connection betweenthe anode of said one device and the grid of the second device, aconnection through an interstage network from the anode of said onedevice to the cathode of said second device, saidnetwork having aresistive component the potential drop across whichprovides biasingpotential for the grid of said second device, a condens er connectedbetween said cathodes, a third electron discharge device comprising acathode, an anode, an input control grid,and a screen grid, and aconnection from the cathode end of said interstage network to saidscreen grid.

7. An electric wave amplifiercomprising a pair of electron dischargedevices each having a cathode, an anode and an input control grid, asource of space current connected between the cathode of one device andthe anode of the second device, a direct connection between the anode ofsaid on'e device and the grid of the second device, a connection throughan interstage network from the anode of said one device to the cathodeof said second device; said network hav- :ing a resistive component thepotential drop across which provides biasing potential for the grid ofsaid second device, a third e1ectrdn discharge device comprisingacathode, an anode, an input controigrid, a grid auxiliaryto saidcontro1 grid, and a connection from the cathode end of said interstagenetwork to said auxiliary grid.

8. A transmssion system comprsing an unattended repeater station, a.plurality of electric wave amplifiers at sad station, each 'amplifiercomprising a pair of electron discharge devices With their space currentcrcuts connected in series such that the space current in each is thesame, each amplfier also comprising an output multigrd electrondischarge device, a pair of power supply conductors connecting theunattended. station Wth another repeater station in sad system wherebypower supply for the amplifiers at the unattended station is providedover said conductors from said other station, a connecton from onesupply conductor to the cathode of the first of sad series-connecteddevices and a connection from the other supply conductor to the anode ofthe second of said series-connected devices, the cathode and the anodeof the output devce being connected across the supply conductors, saidamplifiers beng connected in multiple at a point in the circut of eachintermedate said seres-connected devices to equalize for dflerences inthe characterstics of the devices successively employed in the seriesspace current circuts portion of said amplifiers, and a connection fromsad intermediate point in each amplifier to a grd of its respectveoutput device to provide operating potential for said grid.

9. A transmisson system comprising a multiplicty of eleotric waveamplifiers, each amplifier comprisng a pair of electron dischar-gedevices having a cathode, anode and input grid and with their spacecurrent crcuits cnnected in series such that the space current in each sthe same, each amplifier a1so comprisng an output de'vce, a common powersupply for sad. amplifiers, connections for applying the full potentialof said supply between the cathode of the first and the anode of thesecond of the series-connected devices of each amplifier, and betweenthe cathode and the anode of said output devce, said output devicecomprising also an input control grid and an auxiliary grid, saidamplifiers being connected in multiple at a point in the circuit of eachintermediate said seres-connected. devices to equalize for differencesin characteristics of the devices successively employed in the seresspace current circuts por-tion of said amplifiers, and a connection fromsaid intermediate point in each amplifier to the auxiliary grd of itsrespective output device to provide operating potential for saidauxiliary grid.

10. A11 electric wave circuit comprising a. plurality of electrondischarge devices each comprising a cathode, an anode, and an inputcontrol grid, said devices having their space current'circuits connectedin series such that the space current in each device is the same,another discharge device whose space current circuit is independent ofthat of said plurality of devices and having a grid auxliary to itsinput control grid, and a connection from a point in sadseries-connected devices to said auxiliary grid to provide,

operating potential for said auxiliary grid.

JOHN B. MAGGIO.

